Bulb for mercury switches and the like



J. EFTHER March 22, 1960 BULB FOR MERCURY SWITCHES AND THE LIKE FiledFeb. 18, 1959 4 Sheets-Sheet 1 INVENTOR Jaw [Fr/we ATTORNEY March 22,1960 J. EFI'HER 2,929,889

BULB FOR MERCURY SWITCHES AND THE LIKE Filed Feb. 18, 1959 I 4Sheets-Sheet 2 IN VENTOR c/fA/V [Ff/ ITA BY $1 M;

ATTORNEY March 22, 1960 J. EFTHER 2,929,889

BULB FOR MERCURY SWITCHES AND THE LIKE Filed Feb. 18, 1959 4Sheets-Sheet 3 INYENTOR (/54/1 [ff/ya? ATTORNEY Map-ch 22, 1960 J.EFTHER 2,929,889

BULB FOR MERCURY SWITCHES AND THE LIKE Filed Feb. 18, 1959 4Sheets-Sheet 4 INVENTOR c/fA/V [F 7/7 52 BY V4 ATTORNEY United StatesPatent BULB FOR MERCURY SWITCHES THE LIKE Jean Either,Montr'euil-sous-Bois, France Application February 18, 1959, Serial No.794,054 Claims priority, application France February 28,1958 1 Claim.(Cl. 200-33) The present invention relates to bulbs for mercury switchesand the like.

It has for its primary object the execution of these bulbs in a mannersuch that their manufacture may be simplified and be thus lessexpensive, while providing perfect reliability for the operation of saidbulbs.

It is a well-known fact that mercury does not wet certain materials, inparticular iron, nickel and the like. Thus, considering a metal barhaving an angular crosssection forming a sharp ridge, the angle of thecrosssection of said bar being equal to a, as shown in Fig. 1 of theaccompanying drawings, and assuming the bar is dipped in a mercury bath,as shown on a large scale in said Fig. 1, the mercury will engage thebar along its lateral surfaces but will leave a free space along theridge, the cross-sectional area of said space having a value S dependingon the value of the angle oz.

If it is desired to produce a predetermined loss of head between theends A and B of a mercury-filled tube, as 35 shown in Fig. 2, it issufficient to connect A and B through an inner auxiliary guiding memberconstituted by a bar having the cross-section referred to hereinaboveand providing consequently a restricted crosssectional area for gasesbetween A and B.

In order to allow the invention to be more clearly understood, referencewill now be had to the accompanying drawings given by way of example andwherein:

Figs. 1 and 2 are, as already mentioned, explanatory figures.

Figs. 3 and 4 show, in perspective view, two bars which may be used forthe purpose specified.

Fig. 5 is a further explanatory figure.

Figs. 6 to 13 show various embodiments of a mercury-containing bulbconstituted by two interconnected capacities and incorporating theinvention.

Turning to Fig. 3, it shows a metal bar folded into V shape, while Fig.4 shows a metal rod t in the periphery of which one or more V-shapedgrooves have been cut in parallelism with its axis. Such bars or rodsmay be bent into any desired shape and be immersed in the mercury bath,the mercury not entering or entering only incompletely the folds orgrooves of such bars or rods.

It is also a well-known fact that in the case a glass bulb is used forinstance, which contains mercury and a gas under a certain pressure P,as illustrated in Fig. 5, and includes a restricted medial section d,the pressures P1 and P2 in the two capacities are equal when the bulb istilted round its throttled section. Gravity then produces a flow ofmercury from the capacity 2 into 6 the capacity 1 located in theposition illustrated, but this flow will stop after a very short timebecause the operative volume of the capacity 1 will have been reduced bya drop or drops of mercury entering the capacity 1, while the operativevolume of the capacity 2 increases 70 correspondingly, and therefore thepressure P1 in the capacity 1 will be larger than the pressure P2, whichstops any further flow of mercury into the capacity 1.

Now, there is inserted inside the bulb, as illustrated in Fig. 6, aguide, according to the invention, constituted for instance by the rod tillustrated in Fig. 4; the pressures P1 and P2 will balance each other,after a time depending on the loss of head which is defined in its turnby the number and size of the V-shaped grooves formed in said rod, sothat the flow of mercury from the capacity 2 into the capacity 1 will beobtained at a corresponding speed.

According to the invention and if it is desired to obtain under the sameconditions as precedingly a speedy flow from the capacity 2 into thecapacity 1, it is sufficient, as illustrated in Fig. 7, to close up thepassageway 2 leading to the throttled section and which is designed in amanner such that the mercury cannot enter said passageway which allowsthus a substantial opening for the flow of gas between the twocapacities. To form such a passageway e, it is sufficient to bend theend of the rod 2 in a manner such that the bent end matches the shape ofthe partition d defining the throttled section, said bent end extendingat a small distance from the partition d inside the container 2 whilethe other end of the rod projects partly beyond the level of the mercurycontained in the capacity 1 of the bulb. Thus, such a simple or striatedgroove or rod t which is bent and suitably positioned allows a slow flowof mercury from the capacity 1 into the capacity 2 and a speedy returnfiow from the capacity 2 into the capacity 1, according to the directionof tilting.

Through this arrangement, it is possible to produce switches adapted foruse in many applications, chiefly when it is desired to obtain a delayedbreaking of a circuit and a rapid closing thereof or reversely a speedybreaking and a delayed closing or else when it is desired to obtain botha delayed breaking and a delayed closing.

Figs. 8 and 9 show, on a very large scale, respectively the same bulb asin Fig. 7 in its delayed circuit breaking position and in its positionoccupied at a moment preceding immediately the rapid closing of thecircuit, said switch including as precedingly a rod providing amultiplicity of capillary ducts for the passage of the gas, in a mannersimilar to the rod illustrated in Fig. 4.

In the case of bulbs wherein the flow of gas between the two capacitiesis ensured in the conventional manner by a bundle of two or more twistedwires forming a plurality of capillary ducts and the cross-section andnumber of which are selected in conformity with the magnitude of theloss of head to be obtained, the rigidity of said wires is poor and itis necessary, according to the invention, to give a portion of them asulficient rigidity, so as to obtain a correct and permanent positioningof the bundle inside the bulb, chiefly as concerns the section of thecapillary system lying near the transverse partition 3 defining thethrottled section and correspending to the partition d in Figs. 7, 8 and9.

Figs. 10 and 11 illustrate respectively in a delayed circuit-breakingposition and in a speedily obtained closing position, a bulb insidewhich the guide 4 is constituted by a capillary system formed in aconventional manner by a bundle of twisted wires extending at a distancee from the transverse partition 3 through which is formed a passageway5a; in order to provide permanency of the location of said guide, atubular member 5 is fitted over one end of the latter. Said tubular ele-5 ment is advantageously shiftable to allow an adjustment of thethroughput of the gas 2 into the capacity 1.

Laboratory experiments have shown that by extending the small tube 5 atits lower end 6 beyond the partition 3, as shown in Figs. 12 and 13illustrating said modification, said tube cooperates efficiently infurthering the passage of the gas from the capacity 2 into the capacity1, whereby the closing action of the circuit is increased.

passing out of the capacity When the circuit is actually closed, thisextension of the tube 5 is immersed inside the body of mercury (Fig. 13)and has no further action, since only the capillary system forming theguide 4 provides a passage of gas from the capacity 1 into the capacity2, so as to delay the subsequent breaking of the circuit.

What I claim is: e

A mercury switch comprising a tiltable insulating enclosure, a partitionwall dividing the enclosure into two chambers with a restrictedpassageway therebetween, mercury and gas in said enclosure, said mercurynormally lying in one of the chambers, a plurality of gas capillariescomprising a bundle of twisted wires formed of material nonwettable bymercury and extending from one chamber into the other, a tubular elementfitted over said twisted wires inside one of the chambers and Secured inparallel with said partition wall and at a fixed distance therefrom,said tubular element extending into the other of said chambers slightlybeyond the restricted passageway and secured therein, said capillariesallowing the gas to flow from one chamber to the other therebysubstantially increasing the flow of mercury from one chamber to theother upon tilting of said switch, and a plurality of contacts extendingthrough one of said chambers into contact with the mercury therein whenthe majority of the 10 mercury is in one of said chambers.

References Cited in the file of this patent UNITED STATES PATENTS MeyerIan. 22, 1 952

